1. Technical Field
This invention relates generally to ceramic capacitors, and more particularly to a multi-layer ceramic capacitor (MLCC) device that provides more functionality while requiring less printed circuit board space.
2. Description of Related Art
A typical MLCC device is a tiny electronic component having spaced-apart capacitor electrodes in the form of electrically conductive layers embedded in interleaving and overlapping relationships within a ceramic chip. The manufacturer often produces batches of such devices using green dielectric ceramic tape on which a worker has printed the electrically conductive layers in desired patterns. After layering multiple pieces of the green dielectric tape into a single multi-layered sintered ceramic sheet, the worker dices the single sheet into multiple MLCC devices. Thereafter, the worker terminates the capacitor electrodes at opposite ends of each device with metallization or other electrically conductive material. The resulting MLCC devices typically have dimensions on the order of 10 mils to 120 mils wide and long by 4 mils to 60 mils thick (a mil being equal to one thousandth of an inch).
To mount such an MLCC device on a printed circuit board (PCB), an assembler connects the device terminals to landing pads on the PCB. The MLCC device has a bottom facing the PCB, an oppositely facing top, a front side, a back side, and oppositely facing left and right ends, with the device terminals being located on the left and right ends. The assembler typically uses well known reflow soldering and/or conductive epoxy techniques to provide both electrical and mechanical connections to the terminals. Although effective in some respects, connecting the device that way results in a loss of PCB space. The volume of solder between the capacitor terminals and the landing pad on the PCB (i.e., the “solder fillet”) takes up room around the device. Space must be left between adjacent capacitors to allow placement on the PCB. Moreover, the PCB board is manufactured with extra space between the PCB landing pads so that the solder fillets do not interconnect and make unwanted connections between landing pads and components.
Previous attempts to alleviate space-related shortcomings of existing MLCC devices include using an MLCC array. The array includes multiple discrete capacitors that are printed together and sintered into one monolithic block. The capacitors are lined up next to each other in the device (side-by-side) and terminations are made on opposite ends of the capacitors using a striping machine or other method to print. Another method involves gluing discrete capacitors together with a drop of epoxy adhesive. Both of these methods require fewer devices on the PCB for a given number of capacitor components, and thus they reduce space. However, packing of the devices on a PCB is still limited by the proximity of the landing pads and the solder fillets required for a good bond to the PCB.